This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Brain tumors in rats will be imaged by MI through the scalp and scull, through the scull, and after craniectomy. This is done to study the potential of MI to image tumors covered by normal tissue layers. Tumors will also be imaged after photodynamic therapy. This is done to study the potential of MI to monitor treatment response by functional imaging of blood content and oxygenation. The brain tumor bearing rats are part of an ongoing study at the BLI.